|Covid-19|April 17 – Canute IV succeeds as king of Denmark on the death of his brother Harald III.
May 14 – William Walcher, Bishop of Durham, is killed by rebel Northumbrians. To punish the rebels, King William I of England sends his half-brother Odo of Bayeux to pacify Northumbria.
July 5 – Ísleifur Gissurarson, the first bishop in Iceland, dies while giving mass in Skálholt church.
Autumn – King William I of England's son Robert Curthose is sent to invade Scotland; he reaches as far as Falkirk.
October 14 – Battle on the Elster between the armies of the two rival brothers-in-law kings of the German states, Henry IV, King of the Romans and Rudolf of Rheinfelden meeting at the White Elster river in the Great Saxon Revolt civil war of the Holy Roman Empire. Rudolf is the victor but dies the following day at Merseburg of wounds received.
King William I of England, in a letter, refuses to accept Pope Gregory VII as his overlord.
King Alfonso VI of León and Castile establishes Latin liturgy in the Catholic Church in place of the Mozarabic Rite.
Osmund (bishop of Salisbury), builds Devizes Castle in England.
c. 1080–1100 – The Master of Daphni creates the mosaic of Christ Pantocrator in the central dome of the katholikon at Daphni Monastery in Greece.
The Rubenid Principality of Cilicia gains independence after its founder, Ruben I, Prince of Armenia, succeeds in establishing his authority in the mountainous regions of Cilicia (approximate date).
The Seljuq-led Turkish tribes begin the Great Turkish Invasion of the Kingdom of Georgia.
The Song dynasty Chinese polymath scientist and statesman Shen Kuo begins his defensive military campaign against the Tangut people of the Western Xia Kingdom, successfully defending the invasion route to Yan'an.
The Almoravid emir, Yusuf ibn Tashfin, conquers Tangier, Badis and Hunayn.
Adolf III of Berg (d. 1152)
Teresa of León, Countess of Portugal, Portuguese regent (d. 1130)
April 17 – King Harald III of Denmark (b. 1041)
May 14 – William Walcher, Bishop of Durham
July 5 – Ísleifur Gissurarson, Icelandic bishop (b. 1006)
October 15 – Duke Rudolf of Rheinfelden, leader of the Great Saxon Revolt (b. c.1025)
Year 1080 (MLXXX) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar.
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